1. Field of the Invention
The present invention relates to an optical switch employed for switching optical paths in an optical communication system and a method of manufacturing the same.
2. Description of the Background Art
A conventional optical switch 90 will be described with reference to FIG. 21. This optical switch 90 is one shown in TuM1 (J. E. Fouquet, xe2x80x9cCompact optical cross-connect switch based on total internal reflection in a fluid-containing planner lightwave circuitxe2x80x9d) at OFC 2000 (Optical Fiber communication Conference, Mar. 7, 2000). Optical switch 90 is formed by a silica planar optical circuit substrate 51, where a two-dimensional optical circuit is formed by providing a rectangular optical waveguide having a slightly high refractive index within silica planar optical circuit substrate 51. Generally, silica planar optical circuit substrate 51 having a refractive index of about 1.5 is employed, while optical waveguide 91 portion is made of a material with a refractive index that is higher by about 1%. The portion of optical waveguide 91 is in general also referred to as a xe2x80x9ccore.xe2x80x9d A trench 52 is formed such that it traverses a position that partially overlaps with a crosspoint of optical waveguide 91, and trench 52 is filled with refractive index-matching oil 56. Refractive index-matching oil 56 is oil having a refractive index equal to that of optical waveguide 91.
An operation of optical switch 90 will be described. In optical switch 90, a bubble generating mechanism, not shown, is provided which can generate a bubble 53 and also make bubble 53 disappear in the liquid of refractive index-matching oil 56 at a cross point of optical waveguide 91. For the bubble generating mechanism, as that used for a head of bubble-jet printer may be employed.
When bubble 53 is generated at a crosspoint, a light that enters into the crosspoint is totally reflected by a surface of bubble 53, while when no bubble 53 exists, the light travels in a straight line because optical waveguide 91 and refractive index-matching oil 56 have an equal refractive index. By utilizing this property, an optical path can be switched between two states of reflection/straight travel by generation/disappearance of bubble 53.
In optical switch 90 formed in the above-described manner, accuracy of an etching process requires a width of trench 52 to be at least about 15 xcexcm. In addition, there is a problem of optical loss of at least 0.07 dB per crosspoint. On the other hand, optical loss L [dB] of optical switch 100 as a whole is given by the following formula:
L=2C+(mxe2x88x921)T+(n+1)T+R,
where m is a number of input ports,
n is a number of output ports,
C is a loss [in dB] upon entry of a light into an optical switch from an optical fiber and during travel through an optical waveguide to an active area which is a crosspoint,
T is a loss [in dB] upon traversing one trench and during transmission through a section of a short optical waveguide between two crosspoints, and R is a loss [in dB] for reflection upon a sidewall of an empty trench and transmission through a section of a short optical waveguide between two crosspoints.
For instance, when configuring a large-scale 1000xc3x971000 optical switch, specific numerical values substituted into the above formula give L=2xc3x970.25+(1000xe2x88x921)xc3x970.07+(1000xe2x88x921)xc3x970.07+2.1=142.46 dB. Thus, even with an ideal produced optical switch, optical loss of 142.26 dB would occur. It is necessary to limit optical loss L to 10 dB or below in order for an optical switch to function without degrading signal quality. In this manner, there is a disadvantage in that a larger scale than about 32xc3x9732 is difficult to form with such type of configuration when optical loss is considered.
Moreover, silica planar optical circuit substrate 51 is produced by a device similar to that which produces a semiconductor so that a large optical switch would disadvantageously become extremely expensive to produce. Further, since bubble 53 is produced and utilized each time it is needed in refractive index-matching oil 56, there is a problem of optical switching malfuntion occuring when the generated bubble 53 is too small or when the bubble is generated out of position. Furthermore, depending on the condition of refractive index-matching oil 56, local absorption of light would take place with a small globule of refractive index-matching oil 56 such that an optical path in its periphery would disadvantageously burn due to the energy of a signal light.
An object of the present invention is to provide an optical switch and a method of manufacturing the same that make accurate connect between optical waveguides and optical fiber members possible with easy operation, at the same time, providing an optical switch that facilitates production, that can be formed in large scale with little optical loss, and that does not involve switching malfunction or burning as described above.
In order to attain the aforementioned object, the optical switch according to the present invention comprises a sheet-type main member including a plurality of first optical waveguides linearly extending to intersect with each other on a plurality of intersections therein and optical waveguide means, while the aforementioned main member and the aforementioned optical waveguide means are connected with each other through a connection member, the aforementioned main member has notches provided to traverse the aforementioned first optical waveguides, the aforementioned connection member includes a plurality of second optical waveguides linearly extending for transferring optical signals between the aforementioned first optical waveguides and the aforementioned optical waveguide means therein, the aforementioned main member and the aforementioned connection member are divided from a member continuously formed on the same substrate, and the aforementioned first optical waveguides and the aforementioned second optical waveguides are obtained by dividing optical waveguides continuously formed on the same substrate. According to this structure, the optical switch is formed by re-connecting members divided from a continuous member with each other, whereby the optical waveguides can be correctly aligned with each other along the perpendicular direction by a simple method in the optical switch.
According to the present invention, a mark for relatively aligning the aforementioned main member and the aforementioned connection member with each other is preferably arranged on the connected portion between the aforementioned main member and the aforementioned connection member. According to this structure, the main member and the connection member can be aligned with each other while visually recognizing the mark for connecting the members with each other, whereby the optical waveguides can be readily horizontally aligned with each other in the optical switch.
In order to attain the aforementioned object, the method of manufacturing an optical switch according to the present invention comprises an optical waveguide forming step of forming a polymer layer including an optical waveguide therein on the surface of a substrate, a polymer layer dividing step of dividing the aforementioned polymer layer into a main member and a connection member, and a member connecting step of connecting the aforementioned main member and the aforementioned connection member with each other. According to this method, the single polymer layer is divided into the main member and the connection member, which in turn are thereafter re-connected with each other, whereby optical waveguides can be aligned with each other through a simple operation.
According to the present invention, the method preferably further includes a subassembly assembling step of obtaining a subassembly by connecting the aforementioned connection member with optical waveguide means after the aforementioned polymer layer dividing step and before the aforementioned member connecting step and a notch forming step of forming a notch to traverse the aforementioned optical waveguide in the aforementioned main member, and the aforementioned member connecting step preferably connects the aforementioned subassembly and the aforementioned main member with each other thereby connecting the aforementioned main member and the aforementioned connection member with each other. According to this method, correct alignment can be readily performed without introducing light.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.